Yeah. My entire experience of Snap! is at 1.5, partly because it's better for publication and partly because I'm old. So I bet there are any number of UI issues at 1.0 that I've never seen (along with the ones in flat design).
But imho people can recognize even the thinnest of borders as being borders. For example, never mind the ring, look in your example picture at the border around the IF block. Very thin, but very noticeable.
P.S. Remember that the point of zebra coloring isn't to look nice; it was really meant for cases such as
in which it's just impossible to follow the borders of blocks along the top and bottom edges. In this picture, with only monadic functions, the grouping is obvious anyway, but try it with the dyadic operators +−×÷.